Infra-red vidicon

ABSTRACT

An infrared vidicon utilizing a photo-emissive cathode from which the target of the vidicon is scanned to detect infrared radiation in the intermediate infrared region.

0 United Sfiafies Patem [151 3,675,117 1 Choisser July 4, 1972 INFRA-REDVIDICON 1 References Cited 72 Inventor: John P. Choisser, 8487 Paseo DelOcaso, UNITED STATES PATENTS La Jolla, Calif. 9203'; 3,596,097 7/1971Robillard ..250 83.3 HP

. 3,056,062 9 1962 Garbuny 6131.... ...250/83.3 HP [221 Oct-10,19692,929,868 3/1960 Leiter ..l78/7.2 x 21 APPLNQI 71 399 3,106,605 10/1963Mayo ..178/7.2 X

Primary ExaminerBenjamin A. Borchelt 52 US. Cl ..315/10, 250/833 R,250/83.3 HP, Amid"! Binnie 250/715 S Attorney-Richard K. Macneill 511mm. "H0lj39/00,H01j 31 26 57 A TRACT [58] Field 61 Search ..250 71.5 s,83.31 R, 83.3 11, 1 BS 250/833 HP; 313/65 A, 101, 94; 178/72; 315/10 Aninfrared vidicon utilizing a photo-emissive cathode from which thetarget of the vidicon is scanned to detect infrared radiation in theintermediate infrared region.

2 Claims, 1 Drawing Figure PA'TENTEDJUL 41972 IN VEN'TOR JOHN P. 040/5551? INFRA-RED VIDICON BACKGROUND OF THE INVENTION The presentinvention relates to an infrared vidicon and more particularly to aninfrared vidicon utilizing a photo-emissive cathode as a target-scanningsource.

Prior art infrared vidicons for detecting the intermediate infraredregion; i.e., 1.5 microns to microns, have been plagued by the necessityof shielding the electron source and target from ambient infraredradiation, such as would be experienced with a normal thermionicemissive cathode. This has resulted in many complex implementations,such as that disclosed in an article by R. W. Redington and P. J. VanHeerden, entitled: Doped Silicon and Germanium Photoconductors asTargets for Infrared Television Camera Tubes in the Journal of theOptical Society of America, Volume 49, Number 10, Pages 997-1001. Atbest, these efforts have resulted in cumbersome, expensive andinefficient implementations in an attempt to solve the problem ofdetection in this infrared region.

According to the invention, a vidicon is provided having aphoto-emissive cathode insensitive to infrared radiation in operableproximity to a target which is sensitive to infrared radiation. Ascanning means is provided to scan the target with electrons from thephoto-emissive cathode in a periodic raster. Optical means are alsoprovided for projecting an infrared image on the target simultaneouslywith the electron beam raster scan.

An object of the present invention is the provision of an infraredvidicon for the detection of infrared radiation in the intermediateinfrared region.

Another object is the provision of an infrared vidicon which isextremely sensitive.

A further object of the present invention is the provision of aninfrared vidicon which does not require infrared shielding between itsemitter and its target.

Still another object of the invention is the provision of an infraredvidicon which is inexpensive to manufacture and extremely efficient.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing in which the sole FIGURE is aschematic representation of the preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWING Referring to the drawing, a vidicontube is shown generally at 11 having an envelope 12, one end of which isin proximity to a target 13. Photo-emissive cathode 14 is mounted inproximity to another end of envelope 12 of vidicon 11. An aluminumreflecting surface 16 surrounds photo cathode 14.

A scanning cathode ray tube 17 having a blue scanning spot emits a bluelight which is focused by a lens 18 through a blue transmitting infraredrejection filter 19 to photo-emissive cathode 14.

Target 13 is coupled to a load 21 which, in turn, is coupled to anoutput terminal 22. Load 21 is located in a coolant reservoir 23 whichhas an intake line 24 and an exhaust line 26. An infrared image istransmitted through a visible rejection filter 27 to the reflectingsurface 16 from which it is reflected onto target 13. A focusing magnet28 focuses the electrons emitted from photo-emissive cathode 14 ontotarget 13.

OPERATION In operation, cathode ray tube 17 is scanned with a rasterwhich is focused onto photo-emissive cathode 14 by lens 18. Infraredrejection filter 19 prevents any heat from impinging upon photo-emissivecathode 14. Photo-emissive cathode 14 will, in turn, emit a raster-typescan which is focused by focusing magnet 28 onto target 13. In theabsence of any infrared radiation impinging upon target 13, the outputfrom target 13 will be a steady d.c. through load 21 which will be seenat the OUWLH terminal 22.

en an infrared image is passed through visible re ection filter 27 andreflected onto target 12 by reflecting surface 16, the output fromtarget 13, as it is scanned, will vary in proportion to the infraredimage since the electrical resistance of the target 13 will vary withthis image. A video output can then be taken at output terminal 22 andreproduced with an indicator having a raster synchronous with theoriginal raster of cathode ray tube 17.

A coolant fed in through intake line 24 to coolant reservoir 23 and outthrough coolant exhaust 26 will prevent target 13 from seeing anyambient temperature variations.

It can be seen that an extremely sensitive infrared vidicon has beenprovided by eliminating a thermionic emissive source and further byreducing the effects of ambient infrared radiation.

It should be understood, of course, that the foregoing disclosurerelates to only a preferred embodiment of the invention and that it isintended to cover all changes and modifications of the example of theinvention herein chosen for the purposes of the disclosure which do notconstitute departures from the spirit and scope of the invention.

The invention claimed is:

l. A vidicon comprising:

a photo-emissive cathode, said cathode being insensitive to infraredradiation;

a target in operable proximity to said cathode, said target beingsensitive to infrared radiation;

a light source in operable proximity to said cathode for causingemission therefrom;

scanning means coupled to said light source for scanning said cathodewith said light source; and

a reflecting surface positioned for projecting an infrared image ontosaid target.

2. The vidicon of claim 1 and further including:

an infrared transmitting visible rejection filter positioned

1. A vidicon comprising: a photo-emissive cathode, said cathode beinginsensitive to infrared radiation; a target in operable proximity tosaid cathode, said target being sensitive to infrared radiation; a lightsource in operable proximity to said cathode for causing emissiontherefrom; scanning means coupled to said light source for scanning saidcathode with said light source; and a reflecting surface positioned forprojecting an infrared image onto said target.
 2. The vidicon of claim 1and further including: an infrared transmitting visible rejection filterpositioned ahead of said reflecting surface.